Adjustable electronic component



c -31. 1961 Rw. SPAU E 3,350.613-

ADJUSTABLE ELECTRONIC COMPONENT Filed, June 10, 1966 2 Sheets-Sheet lM/VE/VTOR ROBERT w. SPAUDE Oct. 31, 1967 R. w. SPAUI DE 3,350,673

ADJUSTABLE ELECTRONIC COMPONENT Filed June 10, 1 966 2 Sheets-SheetINVENTOI? ROBERT W. SPAUDE United States Patent Office 3,350,673Patented Oct. 31, 1967 This invention relates to an adjustableelectronic component apparatus such as is commonly employed for variablepotentiometers, rheostats, capacitors, switches and the like wherein theelectrical properties between two or more terminals may be varied andcontrolled. The invention resides more specifically in adjustableelectronic components that may be compacted within small overalldimensions for use in electronic circuits having a great number ofcomponents confined within small space limitations, or in otherinstances where compactness or light weight are of dominating concern.The invention comprises a casing having a molded rotor positioned withinthe casing and rotational therein, the rotor includes a cavity openingtransverse to said rotational axis and having an inclined top surface; astationary base member positioned within the casing in alignment withthe rotor, the base supporting a plurality of individually spaced apartleads which extend through the base to the exterior thereof, the basefurther supporting a plurality of electrical contact surfaces spacedapart in insulative relationship and facing the cavity, each of saidcontact surfaces electrically engaging the internal end of a lead; anelectrically conductive brush member having a front plane and a backplane and having contacts on the front plane to simultaneously engagesaid contact surfaces on the front surface of said stationary base, thebrush member positionedat least in -part wtihin said cavity androtatable with the rotor such that when the rotor is in the properrotational position said brush contacts bridge said front contactsurfaces; resilient means positioned within said cavity, a roundedmember simultaneously engaging the resilient means, the inclined topsurface of the cavity and handicap resides in fabricating an assembly ofsuch small components. The various components of the structures.

are generally very small and require tedious handling during theassembling process, especially where it is necessary to solder or weldvarious components. Also, manufacturing tolerances of the variouscomponents are generally critical due to the small size and when thetolerances are not held, the structure proves inoperable.

The present design provides a structure which may be very easilymanufactured and wherebyall necessary soldering steps may beaccomplished'prior to assembly of the various components into thecasing. The various components of the apparatus may be individually madein large quantities prior to assembly. Theneach individual component maybe sorted and assembled without the requirement of special tools orfasteners. Also, the design is such that dimensional tolerances of theindividualcomponents is somewhat relaxed without hindering the operationof the apparatus. Accordingly, the apparatus is economical tomanufacture andis rugged in design while maintaining small dimensions. a

The invention further provides an assembly whereby as the brush contactswear, there is automatic compensation for the wear and a constantpressure'maintained between the brush and contact surfaces. The brushand ball assembly constantly engage the brush such that as the contactswear the resilient means, e.g., a spring, expands, thereby maintainingthe rounded member, e'.g., a small ball, against the back plane of thebrush and urging it against the stationary member.

The above advantages and features of this invention will appear in thedescription to follow. In the description, reference is made to theaccompanying drawings in which there is shown by way of illustration avariable resistive element in the form of a potentiometer incorporatingthe principles of this invention.

In the drawings:

FIG. 1 is a perspective view of an assembled potentiometer according tothe principles of the present invention with the back and side surfacesmost evident (assuming that the conductive leads extend from the frontsurface).

FIG. 2 is a cross-sectional view taken along the line 22 of FIG. 1.

FIG. 3 is a perspective view, in part broken away, of a rotor componentincorporated in the potentiometer of FIGS. 1 and 2.

FIG. 4 is a cross-sectional view of the rotor component taken along theline 44 of FIG. 3.

FIG. 5 is a perspective view of a stator component carrying theelectrical leads of the illustrated potentiom eter.

FIG. 6 is a perspective view of a conductive brush in: corporated in theillustrated potentiometer. The back surface of the brush is most evidentwith the front surface hidden from view.

FIG. 7 is a view in perspective of a resistive element of thepotentiometer of FIGS. 1 and 2 and designed to accommodate the brush ofFIG. 6

FIG. 8 is a perspective view of the stator component of FIG. 5 mountedwith the resistive element of FIG. 7.

FIG. 9 is an illustrated exploded view in perspective of thepotentiometer with the back surfaces of the various components mostevident.

FIG. 10 is another exploded view in perspective of the potentiometerwith the front surfaces of the various components most evident.

The embodiment of the invention as illustrated in FIGS. 1-10, inclusive,is in a form suitable for use as a miniaturepotentiometer of the typecommonly employed in communication and control circuits. The illustratedembodiment has been. constructed of dimensions in the order of in heightand width with highly satisfactory mechanical :and electrical results.Theapparatus is designated by a general reference character 1. Thepotentiometer 1 includes a cup-shaped, non-oriented casing 2 having acircular recess therein with an end aperture 3 the center of whichcoincides withthe longitudinal axis of the casing. As will bebereinafter further appreciated, the

' casing 2 serves as ameans of providing strength and maintaining theother components of the potentiometer in properly assembled position.Depending on the atmosphere of the actual application, the casing 2 maybe stamped from a metallic substance or molded of a plastic material.The potentiometer further comprises a substantially cylindrical rotorcomponent, designated by the general reference character 4, positionedcoaxially within the casing 2. The rotor 4 is preferably formed of amolded synthetic resin. Viewing the rotor 4 from the rear surface, bestillustrated by FIGS. 3, 4 and 9, it carries three distinct steps 5, 6and 7. The step 5 forms the'outermost diametrical dimension and itsdiameter is slightly less than the internal diameter of the casing 2thereby permitting the rotor 2 to rotate therein. The rise between steps7 and 6 engages the internal bottom surface of the casing 2 leaving avoid space between the corner of the casing 2 and the rotor 4. The step7 is also of circular cross dimensions with the diameter slightly lessthan the diameter of the aperture 3 thereby permitting the rotor toprotrude therethrough. The rotor 4 carries a slot 8 within the areaprotruding through the aperture permitting a tool, for instance ascrewdriver, to engage and adjust the rotor position. As bestillustrated in FIG. 2, the otherwise void space intermediate steps 5 and6 carries a pliant O-ring 9. The O-ring 9, which may be comprised ofsilicone, neoprene, or other type rubber, simultaneously snugly engagesthe step 6 and the interior surface of the casing 2 thereby providing amoisture seal while permitting rotational movement.

Viewing the front surface of the rotor 4 (FIGS. 3, 4 and 10) a cofiinshaped cavity 10 opens towards the front. The rotor 4 also carries anintermediate step 11 between the outermost step 5 and the cavity 10. Thestep 11 permits rotational engagement with respect to the stationarymembers of the potentiometer 1 which will hereinafter be described indetail. The step 11 further carries a stop member 12 such that the rotor4 cannot be continuously rotated in one direction. The cavity 10 ismolded to include a fiat bottom surface 15 which is parallel with therotational axis and normal to the back planar surface of the rotor 4.Engaging the bottom surface 15 and at an angle slightly greater thanninety degrees is a first back plane surface 16. The surface 16 extendspa-rt way up the back of the. cavity 10 where its top edge engages thebottom edge of a plane surface 17. The surface 17 takes the form of anisosceles-triangularshaped plane facing the front of the cavity 10 andnormal to the bottom surface 15. Engaging each of the equal sided edgesof the plane 17 is the back edge of a first top surface in the form ofan inverted substantially V-shaped surface 19. Each plane of theV-shaped surface 19 merges with a common apex which is positively slopedwith respect to the rotational axis towards the cavity opening. In theillustrated embodiment, thevertex slopes at ap proximately 45 withrespect to the axis of rotation. The top surface 19 does not extend tothe front surface. The front edge of the plane 19 engages the back edgeof a second top surface in the form of an inverted substantiallyV-shaped planar surface 20. Each plane of the V- shaped surface 20merges with a common apex which is parallel with the rotational axis.The front edge of the plane 20 extends to the front surface of the rotor4. Flanking each side of the cavity 10 is a five-edged side plane 21.The bottom edge of each plane 21 is common to a side edge of the bottomsurface plane 15. A rear edge of each plane 21 joins a side edge of theback planar surface 16. A first top edge of each plane 21 joins a sideedge of the V-shaped planar surface 19 and a second top edge engages theside edge of the V-shaped planar surface 20. The front edge of each sideplane of the surfaces 21 is common to the front surface of the rotor 4.

Within the recess of the casing 2 and aligned with the front of therotor 4 is a stationary structure comprising a molded base 30 ofinsulative material, the extreme outer dimensions of which are circularcoinciding with the internal dimensions of the casing 2. The base 30which is best illustrated by FIGS. 5, 8, 9 and 10, carries threeapertures 32, 33- and 34 which are designed to accommodate lead wiresextending therethrough. The front portion of the molded base 30 (seeFIG. 10) carries three stand-off feet 35 which, when a metal casing isincluded, insulate the potentiometer 1 from a mounting surface, forexample a printed circuit board (not shown). Each of the feet 35 carryan exterior step 36 (FIGS. 2, 5 and 8) that extends over the end of themetal casing 2. The step 36, in turn, engages the edge of the casing 2thereby controlling the distance the molded base 30 slides within thecasing 2. Intermediate each of the feet 35, the front edge of the base30 is flattened to rovide an. c e surface 4 37 (see FIGS. 2 and 10). Thesurfaces 37 permit a metal casing 2 to be crimped and engage thesurfaces 37 thereby structurally securing the casing 2 and moldedstationary base 30 in turn preventing the apparatus from pushing apart.

On the rear face of the base 30 facing the cavity 10, are four evenlyspaced positioning ears 38, 39, 40 and 41. The ears each have arcuateouter dimensions coinciding with the internal radial distance of thecasing 2, thereby permitting the casing 2 to fit over the ears andengage the steps 36 of the stand-off feet 35. The interior dimensions ofeach positioning ear form a chord with the chords of adjacentpositioning ears being substantially normal to each other. As will behereinafter described, this permits placement of a square-shapedresistive element within the positioning ears. It may be noted that thepositioning ear 38 carries a molded tip 42. The tip 42 serves inconjunction with the mechanical stop 12 of the rotor 4 to preventcomplete rotation of the rotor 4. Intermediate the positioning ears 38and 39 is an arcuate raised ledge 43. Intermediate the positioning ears38 and 41 is another arcuate raised ledge 44 similar to that of 43 suchthat the aperture opening 33 is intermediate the raised edges 43 and 44.Also intermediate the positioning ears 39 and 41 and intermediate theapertures 32 and 34 is a pair of insulating bumps 45. The raised ledges43 and 44 and the insulating bumps 45 are all of equal height and lessthan the height of the positioning cars 38, 39, 40 and 41, therebyestablishing a flat plane intermediate the positioning ears on which aresistance element may be positioned and supported. Furthermore, theledges 43 and 44 and bumps 45 form the side surfaces of a well so that aset of conductive lead wires 46, 47 and 48 may protroude through theapertures 32, 33 and 34, respectively. The leads 46, 47 and 48preferably comprise a material, such as copper, which is highly conductive, highly bendable and highly susceptible to soldering and welding.As shown, the lead wires are bent at a angle and follow along the backsurface of the base 30 within the well. The leads 46 and 48 each pass onone side of a bump 45 and the lead 48 passes between them, therebyinsulating the leads from one another. The internal end of each lead 46,47 and 48, inclusive, is turnedup at approximately 90". Obviously, theleads 46, 47 and 48 can be preformed before insertion in theirrespective apertures or molded within the stationary base 30.

The illustrated potentiometer carries a film-resistive element 60 (seeFIGS 7, 8 and 9). The element 60 comprises a square-shaped, supportingmedium 61 generally comprised of an insulative ceramic material. Themedium 61 supports a first contact surface in the form of a firedon,arcuate, printed resistive track 62 comprised of a material having adesignated resistance according to the desired design and materialmakeup. Opposite ends of the resistive track 62 terminate at terminationpads 63. The film resistive element 60 further carries a second contactsurface in the form of a collector track 64 comprised of highlyconductive material and illustrated in the form of a fired circularpattern. The center of the circular collector is substantiallyconcentric to the center of the arcuate track 62. The collector track 64extends to a third termination pad 65. The termination pads 63 and 65are preferably of a material, eg gold or silver, which can readilywithstand high temperatures and accommodate soldering or welding.Viewing FIGS. 5, 7 and 8, it may be further appreciated that byextending the termination pads 63 and 65 to the edge of the supportingmedium 61, the leads 46, 47 and 48 may be engaged without providingholes within the medium 61 for the leads to protrude. The terminationpads 63 and 65 are designed to accommodate the turned-up ends of theleads 46, 47 and 48. Also, the embodiment illustrates arectangular-shaped resistive element 60. Obviously, the structure may bedesigned to accommodate arcuate resistive elements or resistive elementsof other shapes. However, with present technology, rectangular-shapedelements are generally more easily andeconomically realized.

The film resistive element 60 is designed to fit within the confines ofthe positioning ears 38, 39,40 and 41 and be supported by the ledges 43and 44 and the insulating bumps 45 with the resistance track 62 facingthe cavity of the rotor 4. The resistance element is positioned suchthat the resistance track 62 is a relatively substantial radial distancefrom the casing 2 thereby realizing high leakageresistance between-thetrack and casing. It may be noted that the corners of the supportingmedium 61 are bare of resistance material or pads. Thus, duringassembly, these corner areas can be contacted by a tool to aid theassembler. For example, a tool may clamp on two corners and also push onthe'element 60 for assembly.

Adhering the resistance element 60 and leads 46, 47 and 48 to the moldedstationary element 30, is an adhesive epoxy 66 which is disposed withinthe well formed by the ledges 43 and 44 and the insulating mumps 45 (seeFIG. 2). The epoxy-66 may be disposed within the well by placing apellet or epoxy preform over one of the leads 46, 47 or 48 after theleads are in position. The pellet is then heated so that it melts andfills the well and the voids around the leads and the apertures 32, 33and 34. Next, the resistance element 60 is positioned. Then the entirestationary assembly may be heated to cure the epoxy 66 and provide asecure unit. The forming of the leads 46, 47 and 48, and anchoring themwith the epoxy provides mounted leads which can withstand substantialabusive handling of the exposed ends without dislocation of the embeddedends in electrical contact with the resistance and collector tracks. Theassembly may then be placed in a solder bath thereby simultaneouslyprovidinga solder connection 67 between each of the pads 63 and 65 withthe appropriate lead 46, 47 and 48.

Within the cavity of the rotor 4 is positioned a resilient'member in theform of a low load rate helical coil spring 70 having a long free lengthand many turns with the longitudinal axis perpendicular to therotational axis of the rotor 4. One end of the spring 70-engages thebottom surface 15. The other longitudinal end of the spring 70 cups aspherical member having a spherical surface portion, the member beingideally in the form of a ball 71. The ball 71 simultaneously contactsthe top surface 19 of the cavity 10 and the back surface of a singlepiece brush member 75 comprised of highly conductive carbon blackmaterial of negligible riesistance. (FIG. 6 is-an enlarged view of thebrush 75.) 'The brush 75 fits within the cavity and has back surfaceedge 76 inclined towards theback of the cavity 10 opposing theinclination of the back surface 19. The back surface of the brush 75carries a substantially V-shaped groove flanked by a pair of inclinedplanes 77, each of which contact the ball 71. The brush 75 has asubstantially V-shaped top surface 79 designed to accommodate theV-shaped top surface of the cavity 10. The front" of the brush 75carries two.

contact feet 80 and 81 separated a radial distance coinciding with'theradial distance separating the resistance track 62and the collectortrack 64 of the resistive element 60. I H I Viewing FIG. 2, when thebrush 75 is in'proper position, the combination ofthe spring 70 and ball71 provides two component forces against the brush 75. .One component offorce urges the brush toward and in contact with the resistance element60 thereby maintaining. low contact resistance between the feet 80 and81 and the associated resistance track 62 and collector track 64 whilethe other component of force is normal to the brush feet 80 and 81thereby maintainingthe-brush feet 80 and 81 properly located on thetracks while rotation-adjustment takes place. The force loading pointsof contact of the ball 71 with the inclined angular'top' surface 19 ofthe' cavity10 and the inclined back surface 77 of the brush "7 5 alsoprovide location locking and keying of the brush 75 within the cavity.The 45 angle of the surface 19 reflects the force of the spring 70.Also, the use of a grooved substantially V-shaped back surface 77 of thebrush 75 and the substantially V-shaped surface 19 of the cavity permitsthe ball to make two points of contactwith each. This, in turn, permitsthe use of a brush with only two feet over the commonly used three footbrush, without sacrificing stability of the brush member. The two footbrush facilitates small size and retains minimum or no backlash betweenthe rotor and brush during rotation adjustment.

. Further, the second substantially V-shaped top plane 20 aids in theassembly process. The springand ball 71 can be preassembled in thecavity 10 and be self-retaining, before the brush or stationary base 30are assembled. When the ball 71 contacts the surface 20, there islittle, if any, force tending to push the ball 70 out of the cavity 10.

On the illustrated embodiment, the engagement of the resistance element60 and the brush 75 maintains the ball 71 against the inclined topsurface 19. The ball 71 is permitted to travel along the inclinedsurface 19 between the normal surface 17 and the top surface 20. Thus,the brush 75 maintains engagement with the res'istance element 60 eventhough the contacts and 81 wear or there are dimensional differences inthe various components. Consistency of brush-contact resistance dependslargely upon the pressure of the brush. against the resistance andcollector tracks. To maintain substantially constant spring pressure,the design permits the use of a low load rate spring 71 having alongfree length and many turns. Such a spring gives little force change withdimension change. Thus, there is substantially constant contact pressurebetween the brush contacts 80 and 81 and the contact surface 62' and 64throughout the fullrange of brush movement along the surface 19. It maybe further noted that the center contact foot 81 hasadimple depression82 at the center. The dimple 82 is intended to prevent poor contact withthe collector track surface 64 which may otherwise result from nowearing (wiping action) and at the same time not create off-center.contacting surfaces that would cause a rotation force component to betransmitted to the brush. Also, the plane 16 makes an angle of slightlygreater than with respect to the plane 15. This is intended to aid inretaining the longitudinal axis of the spring 70 stable while permittingthe spring to expand and compress without rubbing against the backsurface 16.

' Viewing FIGS. 9 and 10, the simplicity of assembling the apparatus canbe appreciated. First, the stator 30 is assembled as previouslydiscussed. That is, the leads 46, 47 and 48 are positioned and securedin place by the epoxy 66.. The. resistance element 60 is then positionedover the epoxy and the epoxy cured. Then the leads are soldered to therespective pads 63 and 65. Dipping into a p solder'bath has been foundto be the most efiicient means of soldering. Obviously, solder stops maybe used during the dipping process to maintain the solder only to thedesired areas of the terminals 63 and 65. When these steps have beenaccomplished, the stator 30 appears as in FIG. 8. The spring 70 and ball71 are then positioned in the cavity 10. The O-ring 9 is then. placedwithin the recess of the casing 2 and the rotor assembly 4 slid intoposition until the step 6 engages the O-ring 9 and the step 7 protrudesthrough the opening 3. Then the brush 75 is set within the rotor cavity10 in the proper location. The stator 30 is then slid within the casing2 until the step 36 engages the end ofthe casing 2. At thispoint, thebrush feet 80 and 81 are in engagement with the contact surfaces 62 and64. Completing the assembly, the casing 2, if metallic, is crimped overthe flattened edge surfaces 37.

' Once assembled, as the rotor 4 isrotated, for example by a toolinserted within the slot 6, the brush 77 bridging the resistance track62 and the collector track 64 rotates varying the resistance between thepad 63 and the pad 65. Rotation is realized in either rotationaldirection and continues until the stop 12 on the rotor 4 engages thestop tip 42 on the positioning ear 38.

It may be noted that the leads 46, 47 and 48 may be positioned toproperly accommodate the grid patterns of standard printed circuitboards. At the present time, the standard grid pattern has holes spacedapart in multiples of 0.025 inch. The above-described potentiometer ispresently being constructed with the outlines of the leads forming anisosceles triangle. The linear distance between the leads 46 and 47 is0.200 inch with the lead 48 equally spaced from the leads 46 and 47 withthe vertical distance being 0.100 inch.

It should also be appreciated that the present invention provides astructure which is small in size while being easy to assemble. Also, thedemensional tolerances, even though there is small size, may berelieved. The economic advantages realized by these features is obvious.Also, the various components of the casing, rotor and stator are ingeneral non-oriented so that little assembly time is spent inpositioning the various components with relationship to one another.

It should be fully appreciated that though the preceding detaileddiscussion has been limited primarily to a potentiometer component, theinvention is by no means so limited. For example, a switch may berealized by making one contact surface of highly conductive material andthe other of at least two sections with one section being of highlyconductive material and the other of insulative material. Thus, thebrush can rotate between bridging two conductive surfaces (on position)and bridging a conductive and insulative surface (off position).Furthermore, a capacitive element could be realized by varying thedielectric value between the terminals as the rotor rotates.

I claim:

1. An adjustable electronic component comprising, in combination:

a cup-shaped casing having a circular recess therein;

a circular rotor having a diameter slightly less than the diameter ofsaid recess positioned within the circular recess and rotational thereinwith the axis of rotation coincident with the longitudinal axis of therecess, the rotor having a cavity which cavity opens to the front faceof the rotor, said cavity having a first top surface positively slopedwith respect to the axis of rotation towards the front of said cavity;

a stationary base positioned With in the circular recess and inalignment with the rotor, the stationary base supporting a plurality ofindividual spaced apart electrically conductiveleads each having a shankportion emerging and extending outward from the base, the base furthersupporting a plurality of contact surfaces radially spaced apart ininsulative relationship with one another, at least two of said contactsurfaces electrically engaging the internal end of a conductive lead;

an electrically conductive brush member having a front surface facingthe stationary base and a back surface, said front surface carryingspaced apart foot contacts with the distance between two of said footcontacts coinciding with the radial distance between two of said contactsurfaces, one of said foot contacts making continuous wiping contactwith one of said contact surfaces, said back surface of the brushextending at least in part within the cavity;

a compressible resilient member positioned within said cavity;

a spherical member simultaneously engaging one end of the compressibleresilient member, the top surface of said cavity and the back surface ofthe brush, the spherical member simultaneously maintaining the resilientmember under compression and urging the foot contacts of the brushmember towards said contact surfaces whereby the brush member ismaintained in locked position within said cavity and rotatable with therotor, and

means for adjusting the rotational position of the rotor within thecasing.

2. The adjustable electronic component of claim 1, in which theelectrically conductive brush member has an inclined back surface, withthe angle of inclination opposing that of said first top surface of saidcavity and sloping towards the back of said cavity.

3. The adjustable electronic component of claim 2 in which the backsurface of the brush member is substantial ly V-shaped with two planesmerging towards a common apex and with the spherical member contactingeach plane of said back surface.

4. The adjustable electronic component of claim 1 in which the cavityincludes a second top surface substantially parallel with the axis ofrotation, the back edge of said second top surface joining the frontedge of said first top surface.

5. The adjustable electronic component of claim 1 in which the first topsurface is substantially V-shaped with two planes merging towards acommon apex which apex is positively sloped with respect to the axis ofrotation towards the front of said cavity.

6. The adjustable electronic component of claim 1 in which the first topsurface is substantially V-shaped with two planes merging towards acommon apex which apex is positively sloped with respect to the axis ofrotation towards the front of said cavity, said spherical membercontacting each plane of said first top surface; and

said cavity includes a second top surface of substantially V-shape withtwo planes merging towards a common apex, the apex of said second topsurface being substantially parallel with the axis of rotation and theback edge of said second top surface joining the front edge of saidfirst top surface.

7. The adjustable electronic component of claim 6 in which theelectrically conductive brush member has a back surface of substantiallyV-shape with two planes merging towards a common apex and the sphericalmember contacting each plane of said back surface, said planes of saidback surface of the brush being inclined at an angle opposing that ofsaid first top surface of said cavity and sloping towards the back ofsaid cavity, said brush further carrying a top surface of substantiallyV-shape for locking engagement with said second top surface of saidcavity.

8. The adjustable electronic component of claim 1 in which thecompressible resilient member is a low load rate spring member having arelatively constant force of expansion while urging the spherical memberalong the first top surface.

9. The adjustable electronic component of claim 8 in which thecompressible resilient member is a low load rate helical spring havingmultiple turns, said spring being positioned within said cavity with thelongitudinal axis of the spring substantially normal to the axis ofrotation and with one longitudinal end supported by a bottom surface ofsaid cavity which bottom surface is substatnially normal to thelongitudinal axis of the spring.

10. The adjustable electronic component of claim 7 in which thecompressible resilient member is a low load rate helical spring havingmultiple turns, said spring being positioned within said cavity with thelongitudinal axis of the spirng substantially normal to the axis ofrotation and with one longitudinal end supported by a bottom surface ofsaid cavity which bottom surface is substantially normal to thelongitudinal axis of the spring, said spring having a relativelyconstant force of expansion while urging the spherical member along thefirst top surface.

11. The adjustable electronic component of claim 10 in which said cavityincludes a back surface joining the bottom edge of said first topsurface and the edge of the 9- back surface, the bottom surface and backsurface of the cavity joining at an angle greater than ninety degrees.

12. An adjustable electrical resistance component comprising, incombination:

a cup-shaped casing having a circular recess therein;

a circular rotor having a diameter slightly less than the diameter ofsaid recess positioned within the circular recess and rotational thereinwith the axis of rotation coincident with the longitudinal axis of therecess, the rotor having a cavity which cavity opens on the front faceof the rotor, said cavity having a bottom surface plane radially spacedfrom the axis of rotation and a first top surface positively sloped withrespect to theaxis of rotation towards the front of said cavity;

a stationary base positioned within the circular recess and in alignmentwith the rotor, the stationary base supporting a plurality of individualspaced and apart electrically conductive leads each having a shankportion emerging and extending outward from the base, the base furthersupporting a collector track and aresistance track radially spacedapartin insulative relationship with one another, said collector trackand said resistance track being concentric and facing said cavity, saidcollector track electrically engaging the internalend of one of saidconductive leads and said resistance track electrically engaging theinternal'end of at least one of said conductive leads; i

an electrically conductive brush member having a front plane facing thestationary base and a back plane, said front plane carrying spaced apartfoot contacts with one foot contact making wiping engagement with saidcollector track and another foot contact making wiping engagement withsaid resistance track, said back plane of the brush extending at leastin part within the cavity;

a compressible resilient member positioned within said cavity;

a spherical member simultaneously engaging one end of the resilientmember, the first top surface of said cavity and the back surface of thebrush member, the spherical member simultaneously maintaining theresilient member under compression and urging the foot contacts of thebrush member towards their associate-d resistance and collector tracks;and

means for adjusting the rotational position of the rotor within thecasing. v

13. The variable electrical resistance component of claim 12 inwhich theelectrically conductive brush member has a substantially V"-shaped backsurface inclined toward the back of the cavity opposing the angle ofin-- clination of said first top surface.

14. The variable (electrical resistance component of claim 12 in whichthe brush member has a top surface and the cavity carries a second topsurface, said top surface of the brush member and the second top surfaceof the cavity substantially coinciding in contour; whereby the sphericalmember urges said top surface into locking engagement.

15. The variable electrical resistance component of claim 14 in whichthe first top surface of the cavity is substantially V- shaped with twoplanes merging towards a common apex which apex is positively slopedwith respect to the axis of rotation towards the front of said cavity;

the second top surface is substantially V-shaped with two planes mergingtowards a common apex, the apex of said second top surface beingparallel to the rotational axis and the back edge of said second topsurface being common to the front edge of said first top surface;

the top surface of the brush member being of substantially V-shape forlocking engagement with said second top surface; whereby the brushmember can 10 travel within said cavity along the apex of said secondtop surface and said spherical member can travel along said top surface;and the compressible resilient member is a low load rate spring memberhaving an axis of expansion normal to the axis of rotation and having arelatively constant force of expansion while urging the spherical memberalong the first top surface.

16. The variable electrical resistance component of claim 17 in whichsaid cavity has a back surface inter mediate said bottomvsurface andsaid first top surface, the back surface joining said bottom surface atan angle at least slightly greater than ninety degrees.

1 19. The variable electrical resistance component of claim 15 in whichsaid resistor track and collector track are'in the form of afilmsupported by a planar substrate; theresistor track and collector trackeach carrying termination pads extendingto the peripheral edge of saidplanar substrate and electrically engaging the internal end ofrespective conductive leads.

' 20. The variable electrical resistance component of claim 19 in whichthe supporting base forms a well flanked by supporting ledges ofsubstantially equal height,

said ledges supporting said planar substrate; 7

said terminal leads extending along said well with the internal endsadvancing out of said well adjacent the periphery of said substrateand'a respective termination pad.

21. The variable electrical resistance component of claim 20 in whichthe planar substrate is in the form of a rectangle.

22. An adjustable electronic component comprising in combination:

c a casing;

a brush actuator positioned within the casing and movable relativethereto, said actuator having a cavity which cavity opens to the frontface thereof, said cavity having a top surface portion sloped towardsthe front of said cavity;

a stationary base positioned'to enclose the casing, the stationary basesupporting a plurality of individual spaced apart electricallyconductive leads each having a shank portion emerging and extendingoutward from the-base, the base further supporting a plurality ofcontact surfaces spaced apart in insulative relationship with oneanother, at least two of 'said contact surfaces electrically engagingthe internal end of a conductive lead; i an electrically conductivebrush member having a front surface facing the stationary base and aback surface,

said front surface carrying spaced apart foot contacts withthe distancebetween two of said foot contacts coinciding with the distance betweentwo of said contact surfaces, one of said foot contacts makingcontinuous wiping contact with one of said contact surfaces, said backsurface of the brush extending at least in part within the cavity;

a compressible resilient member positioned within said cavity; aspherical member simultaneously engaging one end i of the compressibleresilient member, the top surface portion of said cavity and the backsurface of the brush, the spherical member simultaneously maintainingthe resilient member under compression and 1 1 urging the foot contactsof the brush member towards said contact surfaces whereby the brushmember is maintained in locked position within said cavity and movablewith said actuator; and

means for adjusting the position of the actuator within the casing.

23. The adjustable electronic component of claim 22, in which theelectrically conductive brush member has an inclined back surface, withthe angle of inclination opposing that of said first top surface of saidcavity and sloping towards the back of said cavity.

24. The adjustable electronic component of claim 22 in which the firsttop surface portion is substantially V- s'haped with two planes mergingtowards a common apex which apex is sloped towards the front of saidcavity, said spherical member contacting each plane of said first topsurface; and

said cavity includes a second top surface portion of substantiallyV-shape with two planes merging towards a common apex, the apex of saidsecond top surface being substantially parallel with the back edge ofsaid second top surface portion joining the front edge of said first topsurface.

25. The adjustable electronic component of claim 24 in which theelectrically conductive brush member has a back surface of substantiallyV-shape with two planes merging towards a common apex and the sphericalmember contacting each plane of said back surface, said planes of saidback surface of the brush being inclined at an angle opposing that ofsaid first top surface of said cavity and sloping towards the back ofsaid cavity, said brush further carrying a top surface of substantiallyV-shape for locking engagement with said second top surface of saidcavity.

26. The adjustable electronic component of claim 22 in which thecompressible resilient member is a low load rate spring member having arelatively constant force of expansion while urging the spherical memberalong the first top surface 27. The adjustable electronic component ofclaim 26 in which the compressible resilient member is a low load ratehelical spring having multiple turns, said spring being positionedwithin said cavity with the longitudinal axis of the springsubstantially normal to the axis of rotation and with one longituidnalend supported by a bottom surface of said cavity which bottom surface issubstantially normal to the longitudinal axis of the spring.

218. The adjustable electronic component of claim 24 in which saidcavity includes a back surface joining the bottom edge of said first topsurface portion and the edge of the back surface, the bottom surface andback surface of the cavity joining at an angle greater than ninetydegrees.

29. An adjustable electrical resistance component comprising, incombination:

-a casing;

a brush actuator positioned within the casing and movable relativethereto, said actuator having a cavity which cavity opens to the frontface thereof, said cavity having a bottom surface plane radially spacedfrom the axis of rotation and a top surface portion positively slopedwith respect to the axis of rotation towards the front of said cavity;

a stationary base positioned to enclose the casing, the stationary basesupporting a plurality of individual spaced apart electricallyconductive leads each having a shank portion emerging and extendingoutward from the base, the base further supporting a collector track anda resistance track spaced apart in insulative relationship with oneanother, said collector track and said resistance track being paralleland facing said cavity, said collector track electrically engaging theinternal end of one of said conducive leads and said resistance trackelectrically engaging the internal end of at least one of saidconductive leads;

an electrically conductive brush member having a front plane facing thestationary base and a back plane, said front plane carrying spaced apartfoot contacts with one foot contact making wiping engagement with saidcollector track and another foot contact making wiping engagement withsaid resistance track, said back plane of the brush extending at leastin part within the cavity;

a compressible resilient member positioned within said cavity;

a spherical member simultaneously engaging one end of the resilientmember, the top surface portion of said cavity and the back surface ofthe brush member, the spherical member simultaneously maintaining theresilient member under compression and urging the foot contacts of thebrush member towards their associated resistance and collector tracks;and

means for adjusting the position of the actuator within the casing.

30. The variable electrical resistance component of claim 29 in whichthe compressible resilient member is a low load rate helical spring oflong length and a plurality of turns, said helical spring having one endcupping the spherical member and the other end supported by said bottomsurface of said cavity.

References Cited UNITED STATES PATENTS 3,013,129 12/1961 Root ZOO-11.23X

ROBERT S. MACON, Primary Examiner.

H. HOHAUSER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No3,350,673 October 31, 1967 Robert w. Spaude It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 1, line "44 for "engaegment" read engagement column 4, line 34,for"protroude" read protrude column 5, line 21, for "mumps" read bumpscolumn 9, line 10, for "on" read to line 18, strike out "and; column 10,line 3, after "said" insert first column 11, line 45, for "longituidnal"read longitudinal Signedand sealed' this 31st day of December 1968.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

1. AN ADJUSTABLE ELECTRONIC COMPONENT COMPRISING, IN COMBINATION: ACUP-SHAPED CASING HAVING A CIRCULAR RECESS THEREIN; A CIRCULAR ROTORHAVING A DIAMETER SLIGHTLY LESS THAN THE DIAMETER OF SAID RECESSPOSITIONED WITH THE CIRCULAR RECESS AND ROTATIONAL THEREIN WITH THE AXISOF ROTATION COINCIDENT WITH THE LONGITUDINAL AXIS OF THE RECESS, THEROTOR HAVING A CAVITY WHICH CAVITY OPENS TO THE FRONT FACE OF THE ROTOR,SAID CAVITY HAVING A FIRST TOP SURFACE POSITIVELY SLOPED WITH RESPECT TOTHE AXIS OF ROTATION TOWARDS THE FRONT OF SAID CAVITY; A STATIONARY BASEPOSITIONED WITH IN THE CIRCULAR RECESS AND IN ALIGNMENT WITH THE ROTOR,THE STATIONARY BASE SUPPORTING A PLURALITY OF INDIVIDUAL SPACED APARTELECTRICALLY CONDUCTIVE LEADS EACH HAVING A SHANK PORTION EMERGING ANDEXTENDING OUTWARD FROM THE BASE, THE BASE FURTHER SUPPORTING A PLURALITYOF CONTACT SURFACES RADIALLY SPACED APART IN INSULATIVE RELATIONSHIPWITH ONE ANOTHER, AT LEAST TWO OF SAID CONTACT SURFACES ELECTRICALLYENGAGING THE INTERNAL END OF A CONDUCTIVE LEAD; AN ELECTRICALLYCONDUCTIVE BRUSH MEMBER HAVING A FRONT SURFACE FACING THE STATIONARYBASE AND A BACK SURFACE, SAID FRONT SURFACE CARRYING SPACED APART FOOTCONTACTS WITH THE DISTANCE BETWEEN TWO OF SAID FOOT CONTACTS COINCIDINGWITH THE RADIAL DISTANCE BETWEEN TWO OF SAID CONTACT SURFACES, ONE OFSAID FOOT CONTACTS MAKING CONTINUOUS WIPING CONTACT WITH ONE OF SAIDCONTACT SURFACES, SAID BACK SURFACE OF THE BRUSH EXTENDING AT LEAST INPART WITHIN THE CAVITY; A COMPRESSIBLE RESILIENT MEMBER POSITIONEDWITHIN SAID CAVITY; A SPHERICAL MEMBER SIMULTANEOUSLY ENGAGING ONE ENDOF THE COMPRESSIBLE RESILIENT MEMBER, THE TOP SURFACE OF SAID CAVITY ANDTHE BACK SURFACE OF THE BRUSH, THE SPHERICAL MEMBER SIMULTANEOUSLYMAINTAINING THE RESILIENT MEMBER UNDER COMPRESSION AND URGING THE FOOTCONTACTS OF THE BRUSH MEMBER TOWARDS SAID CONTACT SURFACES WHEREBY THEBRUSH MEMBER IS MAINTAINED IN LOCKED POSITION WITHIN SAID CAVITY ANDROTATABLE WITH THE ROTOR, AND MEANS FOR ADJUSTING THE ROTATIONALPOSITION OF THE ROTOR WITHIN THE CASING.